Phase shifter



| A. KURTZ 2,951,221

PHASE SHIFTER Aug. 30, 1960 Filed Aug. 1. 1955 PHASE SHIFTER y Louis A. Kurtz, Los Angeles, Calif., assigner to Hughes Aircraft Company, Culver City, K of Delawaren Filed Aug. 1, 1955, Ser. No, 525,437 Claims. (Cl. 333-31) This invention relates to ticularly to mechanical tems.

Phase shifting devices employed in microwave systems have heretofore required extensive circuitry or complicated arrangements to provide a wide range of phase shift without .the introduction of excessive loss into the system. Excessive loss has particularly been introduced where mechanical phase Shifters are employed, because of lthe openings needed to provide control and adjustment of the mechanical phase .shifting arrangement.

lt is therefore an object of this invention to provide an improved phase shifter device for microwave systems, which device is simpler and more economical than the devices of the prior art.

Another object of this invention is to provide an im'- proved mechanical phase shifter for microwave systems which, more eihciently than devices heretofore known, provides a wide range of phase shift with relatively low loss of energy.

A further object of .this invention is to provide an improved mechanical phase shifter for microwave systems which may -be efficiently used without phase shift, or with a variable amount of phase shift.

A phase shifter provided in accordance with this invention may utilize an elongated -dielectric channel member movable within -a hollow waveguide, from one end of which outputs are to be taken. Inputs may be provided -to the hollow waveguide member at a point bei tween the output end and the end at which the dielectric channel member is inserted. Two terminating stubs may he coupled to the hol-low waveguide at selected points with respect to the source of input energy. One terminating stub may be so placed as to divent input energy away from the open end and toward the outputterminal when the dielectric channel member is not inserted in the hollow waveguide. The other terminating stub is placed so as to divert input energy to the output terminal when the dielectric channel member is inserted. Thus, whether or not the dielectric channel member is inserted in the hollow waveguide, input energy is diverted away from the open end and toward the output end with little loss. A phase shift may be introduced, however, which is dependent upon the length of dielectric channel member inserted within the waveguide lbetween the source of input energy and the output terminal. The length of channel member thus inserted,- and the resultant amount of phase shift, maybe varied as desired without affecting the elective operation of :the second terminating stub in preventing -the'loss of energy, The dielectric channel member may be so shaped as to match impedances and to otherwise prevent losses within the system. ,Y

The novel 'features of the invention, as well as the invention itself, both as to its organization and method of operation, will best tbe understood from the following description, taken in conjunction -with the accompanying drawing, in which like reference numerals refer to like parts, and in which:

phase shifter devices, and parphase Shifters for microwave sys- Calif., a corporation terminal 1li,l may receive a dielectric Patented Aug. l30, 1960 Fig. 1 is a lsimplified perspective 'representation of one 'arrangement for practicing the invention, iiiclding a dielectric channel member; l

Fig. 2 is a simpliiiedperspective li'eprshttibn f a second arrangement =for practicing the invention, and

Fig. 3 is a perspective view of a dielectric channel member which may be employed in the arrangements of Figs. 1 and 2.

An arrangement for practicing' the invention, referring now to Fig. il, may employ ahollow rectangular waveguide `10 having an output terminall atY one end thereof and having its opposite end open. The end opposite the output terminal 12, herein referred to as the open end channel member 20. The output terminal 12 of the hollow waveguide 10 may be coupled to associated waveguides ahd microwave elements (not shown) and provide energy of variable phase shift thereto. The open end terminalli is in ythis arrangement employed only for reception of the Vdielectric channel member 20. p

The dielectric channelV member 20, which 'may 'be of polystyrene or other dielectric material, is 'shown` .in more detail in Fig. l3. Referring now to Fig. 3,' as well as Fig. l, the dielectric channel member 20 has a cross section, of a'modiiied U'-s`hap`e, with the base of the U kforming a relatively thickcentral web portion 2'2. The side portions 24, 26 or flanges of the modied U section are on each side of and normal to the web` portion ,22. The dielectric channel niem'bei 20 is enteredv into the hol'- low waveguide 10 withv the central web portion 22v in the plane of the' Ibroadfaces -of the hollow waveguide l0, and is slidably movable along the hollow wavt-:giidev 10. The outer dimensions of the channel member 20 are slightly smaller than the inner'A dimensions of the hollow waveguide d0', 4to provide the desiredy sliding iit and at the same time good electrical cooperation. YThe end of the dielectric channel member 20' which lir'st enters the hollow waveguide 10 when the channel member 120 is inL ser'ted from the op'en end .terminal 14 is herein called the entry end or leading edge of the'channel member 20. The entry end may include a notched portion 28 in the web 22 to match impedance's across the boundary fot-med at the end ofthe dielectric'channel.

A second hollow rectangular waveguide, or input wave*- guide 30; is mounted 'between' the' terminals 1:2,y 14` of the hollow waveguide 10. The input wavegiude 30 is normaly to the hollowwavguide and electrically coupled tov itY by an intermediate series-type resonant coupling slot' 32 arranged, as shown, to provide energy from the input waveguide 30 to .the hollow waveguide 10. Input energy of-4 agiven frequency is suppliedl from a source of energy (not shown) to the input 'waveguide' and is to he provided as output,-with a selected phase shift, at the output terminal 12'of the hollow waveguide 10. If desir'ed, the intermediate coup-ling .slot 32 may Ibe mounted within aV rotatable coupling (not shown) to provide selective impedance matching.

First and second teiininating ,stubs 40, 50, each in-the form of a closed end waveguide section, are mounted normal to the hollow waveguide 10 at predetermined points'betwe'en the input waveguide 30 and the open end tenninalv114. The rst and second terminating stubs 40, 50 respectively, are coupled to the hollow waveguide 10 hy series-type resonant cou-piling slots 42, 52 respectively. The spacing between the -'rst terminating stiib 40 centerline and the centerline of the input waveguide '30 where nis any integer and.v )Wis the wavelength of the lnput energy at the given freqliency f in air-filled waveguide. The first terminating stub 40 is thus effective when the hollow waveguide does not include the dielectrical channel member 20, and is therefore referred to wavelengths where AG is the wavelength of energy propagated at frequency f along the waveguide 10 with the .dielectric channel member 2,0 inserted. The length of i Ithe second terminating stub 50 is again an odd number of quarter wavelengths for the given frequency and stub 50. The second terminating stub 50 may also be termed the stub for dielectric lled waveguide, because the second stub 50 is eiective when the dielectric channel member l20 is inserted between the coupling slot 32 of the input -waveguide and the coupling slot 52 of the second terminating stub.

In operation, input energy of a given frequency f is provided from a source of energy (not shown) to the input waveguide 30. lBy the present device, the input energy may be transferred to the output terminal 12 without shift or selectively shifted a controlled amount `in the transfer.

When employed as a simple coupling device without phase shift, the dielectric channel member 20 may be removed from lthe hollow waveguide 10` or withdrawn so that its leading edge is between the coupling slot 42 of the first terminating stub 40 and the open end terminal 14 of the hollow waveguide 10. Thus input energy supplied from the input waveguide 30 into the hollow waveguide 10 anddirected along the hollow waveguide 10 toward the open end terminal 14 encounters no discontinuity until reaching the first terminating stub 40. Such energy sees a short circuit in the direction of the open end terminal 14, because of the placement and length of the rst terminating stub 40. Energy propagated to the coupling slot 42 -for the iirst stub 40 sees an open circuit, and is reeeted from the termination of the iirst stub 40 toward the coupling slot 32 for the input Waveguide 30. Because the spacing of the stub 40 along the waveguide 10 and the length of the stub 40 are both odd numbers of quarter wavelengths the reflected energy travels a multiple of a full wavelength and is recombined with energy from the input waveguide 30, in phase with that energy.

Energy may also be transferred without phase shift in another way, by inserting the leading edge of the dielectric channel member 20 from the open end terminal 14 of the hollow waveguide 10 to a selected point with respect to the input lwaveguide 30. To provide linear phase shift changes the leading edge of the dielectric channel member 20 is inserted past the coupling slot 32 for the input waveguide 30. With the leading edge proximate the coupling slot 32 the input impedance of the device is readily responsive to the position of the channel member 20. Therefore, for linear phase shift the leading edge of the channel member 20 is advanced beyond the transition zone about the coupling slot 32. The velocity of propagation of energy of the given frequency from the input waveguide 30 is slowed by the dielectric channel member 20, causing a change of wavelength from AA (for air-filled waveguide) to AG. Such energy passes the rst terminating stub 40 with little loss because the surface of the dielectric channel member 20 which is adjacent the coupling slot 42 suiciently detunes the slot 42 to render therst terminating stub 40 substantially ineffective. The spacing of the second terminating stub 50, and the length of the second stub 50, are arranged, like the rst stub 40, such that the second stub 50 provides an effective short oircuit when 4the dielectric channel member 20 is coextensive with the energy path between the second stub 50 and the input waveguide 30. Therefore the short circuit eiect of the second terminating stub 50 returns the energy back toward the coupling slot 32 between the input waveguide 30 and the hollow waveguide 10. Because the length of path traversed in going one way to the short circuit at the second terminating stub S0 -is selected in half wavelengths, the energy `arrives at the coupling slot 32 in phase with the energy moving directly toward the output terminal 1-2. Again there is llittle energy loss at the open end terminal 14.

The selection of la desired phase shift is controlled by the extent to which the leading edge of the dielectric ch-annel member 20 is inserted in the hollow waveguide 10 past the coupling slot 32 of the input waveguide 30. The amount of dielectric 20 present between the coupling slot 32 and the output terminal 12 determines Ithe extent of propagation of energy at the slower speeds resulting from the dielectric, thus providing the selected phase shift. Note that ythe dielectric channel member 20 may be calibrated or that some system of Calibrating marks may be used against any selected reference point, so that an amount of phase shift desired may be chosen simply by visual inspection.

In a second form, referring now to Fig. 2, the input waveguide 30 may be disposed at a different angle with respect to the hollow waveguide 10. In this form the broad face of the input waveguide 30 may be parallel to, instead of normal to, the broad face of the hollow waveguide 10. The coupling slot between the two waveguides 10, 30, is therefore a slot 34 disposed at an angle with respect to both waveguides 10, 30. The angle need not be 45, but may =be varied :to match the impedance between the waveguide 10 with and without the dielectric channel member 20. Note also that the terminating stubs 40, 50 may be arranged parallel to the input waveguide 30 of Fig. 3 if desired. v

One phase shifter constructed in accordance with the invention employs a dielectric channel member having a thickness approximately half the height of the guide, with anges 1/16 inchthick. Such a phase shifter provides a phase shift of :21/2 per inch with a variation of coupling of only 10.1 db. A notch 28 in the end of the dielectric channel member 20 forms a quarter wave transformer to match irripedances across the boundary formed at the end of the dielectric channel. Although the present arrangement is described for illustrative purposes as `a single frequency device, it may be noted that a range of frequencies may be covered by utilizing movable terminating stubs 49, 50 which are adjustable over a -band of frequencies. With such as arrangement, however, the calibration of the dielectric channel member 20 would change with the frequency.

Thus there has been described an improved mechanical phase shifter for microwave systems. The arrangement provides a simple and economical phase shifting device of low power loss which is continuously variable over a. range of phase shift values.

What is claimed is:

1. A microwave phase shifter comprising first waveguide means including an output terminal and an open terminal spaced apart at a predetermined minimum distance from said output terminal; input waveguide means coupled to said lirst waveguide means between said output terminal and said open end; rst reflecting means coupled to said first waveguide means between said input waveguide means and said open end at a position an 'odd number of quarter wavelengths in air from said input waveguide means for reecting away from said open end energy in said first waveguide means when said first waveguide means is air lled; second reflecting means coupled to said first waveguide means between said rst reecting means and said open end at a position an odd number of quarter wavelengths in a dielectric medium apsijaai Y Y .t other than air for reflecting away from said open terminal energy in said first waveguide means when the space between said input waveguide means and said second reflecting means includes said dielectric medium; and an elongated member of said dielectric medium selectively movable within said first waveguide means, and .extending from said second reflecting means to a selectable point past said input waveguide means.

2. A mechanical phase shifter for microwave waveguides comprising: a rectangular output waveguide, one end of which provides an output terminal and the other end of which is an open terminal; a dielectric channel member movable within said output waveguide between the terminals thereof, said dielectric channel member including a notched portion at the end closest the output terminal of said waveguide; -a rectangular input waveguide coupled to said output waveguide at a point between the terminals thereof for feeding energy to said output waveguide; a -first terminating stub coupled to said output waveguide at a first predetermined point an odd number of quarter wavelengths in air from the point of coupling of the input waveguide to the output waveguide toward the open terminal of said output waveguide; and a second terminating stub coupled to said output waveguide at a second predetermined point an odd number of quarter wavelengths in said dielectric from the point of coupling of the input waveguide to the output waveguide toward the open terminal of said output waveguide.

3. A microwave phase shifter comprising: an output waveguide having an output terminal and an open end terminal; an input waveguide coupled to said output waveguide between the terminals thereof and providing energy of a given frequency thereto; -iirst means coupled to said output waveguide and spaced at a predetermined distance an odd number of quarter wavelengths in a first medium from said input waveguide toward said open end terminal for diverting away from said open end terminal energy which is propagated at a first given speed in said output waveguide; second means spaced an odd number of quarter wavelengths in a second medium from said input waveguide toward the open end terminal coupled to said output waveguide for diverting away from said open end terminal energy which is propagated at a second given speed in said output waveguide; a dielectric channel member of said second medium movable within said output waveguide for selectively changing, from the first given speed to the second given speed, the speed of propagation of energy from said input waveguide which is directed toward said open end terminal, said channel member having a maximum length greater than the distance between said second means for diverting energy and said input waveguide.

4. A mechanical phase shifter for microwave systems, for shifting the phase of input energy of a given frequency a selectable amount and transferring the shifted energy to an output terminal, said phase shifter comprising: a first hollow rectangular waveguide member providing said output terminal at one end thereof and having an open terminal at the other end thereof; a second rectangular waveguide member responsive at one end thereof to said input energy and having its other end coupled to said first waveguide member at a point between the terminals thereof, the axis of said second rectangular waveguide member being substantially normal to said first waveguide member axis; means including va first series-type resonant coupling slot for transferring energy from said second waveguide into said first waveguide; a first terminating stub coupled substantially normal to said first waveguide at a distance of wavelengths, where AG is the wavelength of wave energy in a dielectric-filled waveguide at the given input frequency; means including a third series-type resonant coupling slot coupling said second terminating stub -to said first waveguide member; and a U-shaped channel member of dielectric material within said first waveguide member and movable longitudinallytherein, the-base of the U-shaped channel member being relatively thick and parallel to the plane of movement of said channel member; said channel member including an impedance matching notch in the end closest to the output terminal, the extent of channel member inserted past the second waveguide member from the open terminal of said `first waveguide member determining the amount of phase shift in input energy provided to said' second waveguide member.

5. A mechanical phase shifter for microwave systems, for shifting the phase of input energy of a given frequency a selectable amount and transferring the shifted energy to an output terminal, said phase shifter comprising: a first hollow rectangular waveguide member providing said output terminal at one end thereof and having an open terminal at the other end thereof; a second rectangular waveguide member responsive at one end thereof to said input energy and having its other end coupled to said first waveguide member at a point between the terminals thereof, the broad faces of said first and second waveguide members being substantially parallel; means including a first coupling slot disposed at an angle to the axis of both said first and second waveguide members; a first terminating stub coupled substantially normal to said first waveguide member at a distance of (2114+ l) AA wavelengths from the point of coupling of said second to said first waveguide members, where n is an integer and AA is the wavelength of wave energy in air-lled waveguide at the given input frequency; means including a second, series-type, resonant coupling slot coupling said first terminating stub to said first waveguide member; a secondl terminating stub coupled substantially normal to said first waveguide member at a distance of wavelengths, where AG is the wavelength of wave energy in a dielectric-filled waveguide at the given input frequency; means including a third, series-type, resonant coupling slot coupling said second terminating stub to said first waveguide member, and a U-shaped channel member of dielectric material within said first waveguide member and movable longitudinally therein, the base of the U-shaped channel member being relatively thick and parallel to the broad faces of said first and second waveguide members, said channel member including an impedance matching notch in the end thereof closest to the output terminal, the extent of channel member inserted past the second waveguide member from the open terminal of said first waveguide member determining the amount of phase shift in input energy transferred to said first waveguide member.

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